In general, vinyl chloride-type polymers are prepared by the suspension polymerization of vinyl chloride monomers or a mixture of vinyl-type monomers with vinyl chloride as a major constituent in an aqueous media using a monomer-soluble polymerization initiator. At this time, the types of monomer-soluble polymerization initiators employed have a large effect on the exothermic pattern during the polymerization reaction, polymerization duration, productivity, and scale deposition during the polymerization, as well as on the quality characteristics of polymers such as initial colorization, thermal stability, odor, and extraction resistance.
Further, recent trends aim to reduce the duration of the polymerization reaction in order to improve the productivity for vinyl chloride-type polymers. Therefore, the amount of polymerization initiators being utilized is increasing. However, the increased amount of utilized polymerization initiators brings up problems: the limitations accompanied by the insufficient cooling capacity of the polymerization instruments in general; the effects on polymer qualities, particularly on the initial colorization, thermal stability, the generation of strange odors caused by the residue of the polymerization initiators, the increased amount of the decomposition products, and the increase in the extractable components; and further the increased amount of scale deposit in the polymerization vessels.